Sea Four is bland. There is nothing very interesting about Sea Four, nothing bad happens and nothing so good does either. In fact, the only thing of note is the canal that was dug to reach Sea Five as there was no previous way to reach said Fifth Sea. The earth that makes up the sea is quite easy to dig into and so has been the spot of many different expiriments in digging technology. There is currently an expidition known as Charlie's Search that uses sea serpents to dig for a cache of diamonds that may or may not exist.